Human-powered vehicles are used as a popular method of transport and exercise. Bicycles and handcycles are examples of human-powered vehicles used by people of many different abilities. A bicycle has two wheels and is powered by a person's legs, whereas a handcycle typically has three wheels and is powered by a person's arms. A handcycle, also called a handbike or hand trike, is propelled and steered through manipulation of the handlebars. The handlebars of a handcycle are coupled to one or more gears which turn a drive wheel or wheels on the handcycle. A rider rotates the handlebars in a crank-like motion to power the handcycle. A rider may operate a handcycle while sitting, kneeling, or reclining in a seat of the handcycle. A rider's legs may rest in stirrups or be secured to the frame of the handcycle. Because handcycles do not require use of the rider's legs, many riders with disabilities can use handcycles.
Handcycles are often designed with one front wheel and two back wheels but may also be designed with other wheel configurations, such as with one back wheel and two front wheels or two front wheels and two back wheels. One common steering mechanism for the handcycle with a single front wheel is called fork-steering. Fork-steering requires the front wheel to turn or tilt with respect to the back wheels. In a fork-steering design, the handcycle frame has two portions. A front frame portion, called the fork, provides a mounting point for the handlebars, gearing, and front wheel. A main frame of the handcycle provides a mounting point for the seat and back wheels. The fork rotates around the front axle with respect to the main frame so that the front wheel can be aimed to steer the handcycle. A rider manipulates the handlebars to turn or tilt the fork in order to steer the front wheel of the handcycle. A rider rotates or cranks the handlebars to turn one or more gears which drive the front wheel and propel the handcycle.
As a handcycle encounters bumps and unevenness in the terrain, the impact of the handcycle hitting a bump is felt by the rider through the handlebars, footrests, and seat of the handcycle. Handcycles may include a rear suspension system which supports weight and absorbs shock at the rear wheels. A rear suspension system may include an independent suspension system, such as double a-arm or wishbone suspension, coupled to the rear of the handcycle frame near the rear wheels. Rear suspension helps the rear wheels maintain contact with the road or terrain when the handcycle encounters unevenness or bumps. Rear suspension systems also provide a smoother ride by reducing vibration of the handcycle frame as the rear wheels encounter rough terrain. However, rear suspension does not adequately address shock or vibration at the front wheel or front fork of the handcycle.
The shock of the front wheel hitting a bump is felt by the rider most dramatically in the handlebars, because both the handlebars and front wheel are mounted to the fork. The steadiness of the handlebars is important on a handcycle, because the rider uses the handlebars not only to steer, but to propel the handcycle. A handcycle rider benefits from handlebars that are as steady as possible during a ride. When the handcycle hits a bump, the vertical change at the front wheel raises the front of the handcycle. The front of the handcycle drops back down as the handcycle traverses the bump. The vertical change at the front of the handcycle causes undesirable motion or vibration in the handlebars and can make holding onto the handlebars and cranking the handlebars more difficult.
The fork at the front of the handcycle provides limited space in which to add parts and features to the handcycle. The fork should be narrow enough to be comfortable for the rider and the fork should be configured to mount the front wheel and gearing components. The fork should also be able to pivot with respect to the rest of the handcycle to allow the rider to steer the handcycle. Added parts and features at the front of the handcycle should not interfere with steering, safety, or the rider's comfort while riding the handcycle.